This application requests funds in support of the Fourth International Symposium on Microsomes and Drug Oxidations to be held at the Towsley Center for Continuing Education on the campus of the University of Michigan, Ann Arbor, Michigan, July 15-18, 1979. The Symposium will cover recent advances in the metabolism of carcinogens, drugs, and lipids by microsomal enzyme systems, with emphasis on the isolation, characterization, mechanism of action and function of cytochrome P-450, and relevant aspects of chemical carcinogenesis. The Symposium will be open to all interested scientists. Based on the broad current interest in cytochrome P-450 and microsomal metabolism, as well as the attendance at previous such meetings, we expect about 300 persons to attend. About 35 outstanding investigators in this field from the United States and abroad will be invited to present lectures. The general plan is for half of each day to be devoted to plenary lectures providing some review of each topic, as well as newer findings, followed by shorter lectures dealing exclusively with new research results. The other half of the day will be devoted to poster presentations on the same topics. We plan to publish the proceedings of the Symposium, including plenary and shorter lectures, discussions following the lectures, and brief papers based on the poster presentations.